title: Visual grading characteristics (VGC) analysis of diagnostic image quality for high resolution 3 Tesla MRI volumetry of the olfactory bulb.
abstract: OBJECTIVE
  The aim of this study was to evaluate the suitability of 3-T magnetic resonance imaging (MRI) for olfactory bulb volumetry, comparing image quality obtained using different sequences on the basis of physical characteristics in combination with observer performance.
  
  
  METHODS
  Twenty-two healthy volunteers (11 men, 11 women; mean age, 25 years) underwent 3-T MRI of the frontal skull base in this prospective study. Imaging was performed using a constructive interference in steady state (CISS) three-dimensional Fourier transformation sequence, a three-dimensional T2-weighted (3D-T2w) sequence, and a two-dimensional T2-weighted (2D-T2w) sequence. The relative performance of sequences was assessed using visual grading characteristic analysis. Interobserver agreement was assessed using κ statistics. For evaluation of physical image quality characteristics, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated and compared using Wilcoxon's test. SNR and CNR measurements were correlated with visual grading results.
  
  
  RESULTS
  Visual grading characteristic analysis showed significantly better image quality ratings for the CISS sequence compared to the 3D-T2w and 2D-T2w sequence, and the 2D-T2w sequence performed significantly better compared to the 3D-T2w sequence (P < .001). Interobserver agreement was substantial (κ = 0.66-0.73). Wilcoxon's test revealed significantly higher SNR and CNR values for the 2D-T2w sequence compared to the 3D-T2w and CISS sequences, and SNR and CNR values for the 3D-T2w sequence were significantly higher compared to those for the CISS sequence (P < .001 for each). Significant correlation between SNR and CNR and visual grading was found for the 3D-T2w sequence (SNR: ρ = 0.510, P = .015; CNR: ρ = 0.546, P = .009).
  
  
  CONCLUSIONS
  High-resolution 3-T MRI resulted in excellent values for SNR and CNR, suggesting the appropriateness of the sequences for olfactory bulb MRI volumetry. Visual grading characteristic analysis revealed the CISS sequence to be the most suitable for olfactory bulb volumetry.
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital, Friedrich Schiller University Jena, Germany. hartmut.burmeister@med.uni-jena.de
authors.forename: Hartmut Peter
authors.initials: HP
authors.lastname: Burmeister
authors.forename: Pascal Andreas Thomas
authors.initials: PA
authors.lastname: Baltzer
authors.forename: Constanze
authors.initials: C
authors.lastname: Möslein
authors.forename: Thomas
authors.initials: T
authors.lastname: Bitter
authors.forename: Hilmar
authors.initials: H
authors.lastname: Gudziol
authors.forename: Matthias
authors.initials: M
authors.lastname: Dietzel
authors.forename: Orlando
authors.initials: O
authors.lastname: Guntinas-Lichius
authors.forename: Werner Alois
authors.initials: WA
authors.lastname: Kaiser
mesh_terms: D000328:Adult; D016477:Artifacts; D005260:Female; D006801:Humans; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging; D008297:Male; D015588:Observer Variation; D009830:Olfactory Bulb / Q000000981:diagnostic imaging*; D009929:Organ Size; D011446:Prospective Studies; D011859:Radiography; D012680:Sensitivity and Specificity